A number of methods for treating a length of textile material, which may be used in reinforced elastomeric products, e.g., a transmission belt, exist in the prior art. One such method involves coating one side of a textile material with low viscosity liquid cement, such as to provide a durable textile material. The low viscosity liquid cement, which can flow at least partially into the fabric, may be prepared by dissolving a small amount of crosslinkable rubber in a suitable solvent. However, when the fabric interstices are filled, removal of the solvent results in shrinkage of the cement and the creation of undesirable voids in the rubber within that fabric. Additional coats of cement can be applied to the same other side of the textile to reduce the voids. The additional coats may use cement containing the same, or a different rubber than the first coat to obtain desired properties on each side of the textile or to improve adhesion to the reinforced elastomeric product. This solvent process only works for soluble rubbers, or for material that can be suspended in the solvent. For example, thermoplastics, such as polyethylene, may not be soluble in typical rubber solvents at atmospheric pressure and suitable temperatures. In addition, solvent evaporation and/or removal is an additional step in this fabric processing and can require additional machinery to handle the solvent. Also, solvent use and the removal and possible incineration of the solvent undesirably increases the energy content, cost and carbon footprint of this process.
Another method for treating a length of textile material includes calendaring crosslinkable rubber compounds onto the textile material. The rubber and textile pass through a small gap between calendar rolls where the rubber is pressed onto the textile with high pressure applied for a short time. Even when softened by heat and shear, the unvulcanized compound has a significant elastic component of viscoelasticity that reduces penetration into the textile material. Thus, the calendared compound can penetrate only the larger interstices of the textile material, and not the smaller interstices. In addition, this process only works for millable elastomers, i.e., those elastomers that can form a continuous mass when subjected to the shear stress applied by the calendar.
Yet, another method includes extruding thermoplastic elastomers onto textile material. In this process, the thermoplastic is melted in an extruder by heat and shear. To reduce viscosity and pressure, the temperature is often well above the melting point of the thermoplastic. The melted thermoplastic then passes as a fluid into a die, which forms the thermoplastic into a film or sheet of suitable thickness. The die may be a coat hanger die or other design suitable for creating the desired shape of the melt stream, which is laid on the fabric or pressed into the fabric by die pressure. However, the flow of the melt in the extruder and die is not uniform for all of the melt. Some portions move faster and some much slower than the average flow. While this process works well for non-crosslinkable materials, it is not suitable for crosslinkable thermoplastics, for example, because the residence time at temperature of the slower moving material exceeds the safe processing time and the material starts to prematurely cross-link.
Accordingly, there is a need for a process to apply crosslinkable thermoplastic elastomer compounds to textile materials which does not use solvents yet achieves penetration into the small interstices of the material, such treated material for use in reinforced elastomeric articles.